Biocards have been used to analyze blood or other biological samples in a spectroscopic or other automated reading machine. Such machines receive a small biocard, roughly the size of a playing card, in which biological reagents, nutrients or other material is deposited and sealed, prior to injection of patient samples.
The biocard contains the reagents and receives the patient samples in a series of small wells, formed in the card in rows and columns and sealed, typically with tape on both sides. The biocards are filled with patient sample material through fine hydraulic channels formed in the card. The microorganisms in the samples may then be permitted to grow or reactions to proceed, generally over a period of up to a few hours, although the period varies with the type of bacteria or other substance analyzed and sample used.
After the incubation, the samples contained in the wells are placed in front of a laser, fluorescent light or other illumination source. The content of the sample in a given well can then be deduced according to readings on the spectrum, intensity or other characteristics of the transmitted or reflected radiation, since the culture of different bacteria or other agents leave distinctive signatures related to turbidity, density, byproducts, coloration, fluorescence and so forth. Biocards and machines for reading them of this general type for use in these biochemical applications can for example be seen in U.S. Pat. Nos. 4,318,994; 4,118,280; 4,116,775; 4,038,151; 4,018,652; and 3,957,583.
Despite the general success of biocards in this area, there is an ongoing desire to improve the performance of the cards and readings on their samples. It is for example an advantage to impress more reaction wells in a given card, so that a greater variety of reactions and therefore discrimination of samples can be realized. A given facility may have only one such machine, or be pressed for continuous analysis of samples of many patients, as at a large hospital. Conducting as many identifying reactions on each sample as possible is frequently desirable, yielding greater overall throughput.
However, biocards that have been exploited commercially have often been limited to a total of 30 sample wells (or 45 wells in some designs). For compatibility with existing reading machines, the cards generally can not be enlarged from a certain standard profile (roughly 31/2" by 21/4"). Total well capacity has accordingly not grown beyond these levels, limiting the throughput on the machines.
It has also been the case that as the total number of reaction wells on a given card has increased, while the card size has remained constant, the wells have necessarily been formed increasingly close together. With the sample wells crowding each other on the card, it has become more likely that the sample contained in one well can travel to the next well, to contaminate the second well. The threat of increased contamination comes into play especially as card well capacity increases above 30 wells.